Electrostatically charged image developing copiers and printers are gaining popularity because of widespread office automation. With this background, demand is growing for high grade or sharp copied images which are highly light transmissive and well fixed.
Under these circumstances, we stated to the following effect in Japanese Patent Application No. 354063/95 (filed Dec. 29, 1995), which was not laid open to the public when the present application was filed: “The relevant problem can be solved or diminished by using a polyolefin resin having a cyclic structure as a binder resin for a toner for heat roller fixing type electrostatically charged image developing copiers and printers, and also by incorporating less than 50% by weight of the polyolefin resin with a high viscosity into the entire binder resin. As a result, a sharp, high quality copied image which is excellent in fixing, light transmission and anti-spent toner effect can be obtained. Particularly when this resin is used in a color toner, its characteristics are exhibited.”
This previous invention, however, was defective in that it was difficult to get a sufficiently broad offset-free temperature range suitable for practical use, and scarcely achieved an enough fixing property at an even higher copying speed to meet users' requirement.
In fixing a toner image onto plain paper or an OHP film, various fixing methods are available, such as hot roller fixing, hot belt fixing, pressure fixing, radiant heat fixing, or flash fixing. In recent years, energy saving symbolized by “Energystar restriction” has been demanded increasingly, and demand has become intense for a toner fixable at a low temperature and a low pressure. The thermal properties and mechanical properties of conventional styrene-acrylate resins and polyester resins, or the polyolefin resins having a cyclic structure described in Japanese Patent Application No. 354063/95 cannot satisfy the requirements at lower temperatures or pressures than the current level. Improvement in the thermal properties of these resins on one hand resulted in the deterioration of storage stability of the toner on the other hand.
General formulations for toners in electrostatically charged image developing copiers and printers are shown in Table 1.
TABLE 1General Formulations of Toners(Unit: % by weight)ChargeFunctionBinder resinColorantcontrol agentimparting agentMagnetic powderSolventDry two-component toner50-1000-200-100-20——Dry nonmagnetic one-50-1000-200-100-20——component tonerDry magnetic one-component 0-1000-200-100-200-60—tonerDry polymerized toner50-1000-200-100-20——Liquid dried toner15-50 0-100-5 0-10—50-70Liquid toner15-50 0-100-5 0-10—50-70
The object of the present invention is to provide a toner in a dry two-component, dry nonmagnetic one-component, dry magnetic one-component, dry polymerized, liquid dried, or liquid toner developer which exhibits the effects achieved by Japanese Patent Application No. 354063/95, is to propose a sufficiently broad offset-free temperature range suitable for practical use, can attain sufficient fixing property even by high speed copying, and gives a higher grade image, namely, good in fixing, highly optically transparent, sharp image in an electrostatically charged image developing copier or printer.